Abstract
The work reported below describes development of a novel method, termed X-ray phase contrast stereometry, for reconstructing the three-dimensional (3D) positions of features within a specimen. The approach takes measured positions of a given feature in phase microradiographs recorded at different viewing angles and refines that feature's position numerically. The approach is designed to address limitations in conventional laboratory or synchrotron X-ray absorption micro computed tomography (microCT), particularly those inherent in studying plate-like samples. The phase stereometric reconstruction technique was applied to a small compact tension sample of aluminium alloy AA 2090 (20.3 mm wide from notch tip to back face and 2.7 mm thick) containing a fatigue crack and was used to map the 3D crack surface non-invasively. Up to ten viewing angles were used for each of 2269 points mapped on the approximately 2.7 mm × 6.0 mm surface. The 3D stereometry-derived crack surface agreed with the surface map from absorption microCT of the same sample. The phase technique was superior in terms of its crack sensitivity; the phase images allowed the crack to be followed to its tip, even with zero applied load while absorption microCT could only detect about 5 mm of the crack 6 mm long when loaded to 40 kgf. The origin of the contrast used for stereometric mapping was confirmed to be from the peaks on the crack face; phase microradiographs from a second (intact) sample showed a pattern of features identical with those revealed on the surface when the sample was split open. Crack opening as a function of in-situ load was measured for the same points on the crack surface using both phase stereometry and absorption microCT; the openings were in good agreement.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 3273-3300 |
| Number of pages | 28 |
| Journal | Philosophical Magazine |
| Volume | 85 |
| Issue number | 28 |
| DOIs | |
| State | Published - Oct 1 2005 |
Funding
The authors dedicate this article to the memory of Professor Howard K. Birnbaum, recently deceased, the thesis supervisor of the corresponding author. His long-time advocacy of synchrotron X-ray imaging, even though he did not work extensively in this field, will be missed. This article summarizes some of the results from the PhD thesis of Ignatiev [51]. The authors thank Dr J.C. Elliott and Dr G.R. Davis (Queen Mary, University of London) for their collaboration on the absorption microCT measurements of sample CT-41M, reported earlier, which allowed the phase stereometric results to be verified. The authors also thank Dr E. Lautenschlager (Northwestern University) for his help fracturing sample CT-33M and Dr J.D. Almer (XOR APS) for his help setting up the in-situ load frame used in this study. The initial stages of this research were partially supported by the US Office of Naval Research (grants N00014-89-J-1708 and N00014-94-1-0306). Use of the APS was supported by the US Department of Energy, Office of Basic Energy Sciences, under contract W-31-109-ENG-38.
ASJC Scopus subject areas
- Condensed Matter Physics